Many emergency situations, and even many non-emergency situations, create a need to rapidly block-off, obstruct, or seal an opening in, or between, structures. For instance, during urban combat or law enforcement activities a route may need to be blocked to prevent an attack by opposing forces, the escape of the opposing forces or the flight of a suspect. These routes are typically characterized by choke points such as narrow alleys or streets, pre-existing openings through structures (e.g., windows or doors), and breaches of the structure (e.g., openings created by an explosive device). Because conditions in the field can change rapidly and because the forces may move about in the field, it therefore becomes desirable to erect the barrier rapidly. Similarly, once the need for the barrier passes it is often desirable to reopen the route so that other activities involving the chokepoint are not unduly hindered.
While many of these situations occur outdoors, many indoor situations also create a desire to obstruct a choke-point or other passageway. For instance, the release of a chemical in an indoor setting (e.g. a manufacturing facility) may cause a desire to seal the area of the facility in which the release occurred. Similarly, a fire or explosion may make it desirable to prevent the outflow of combustion products, and the in flow of air or combustible materials such as natural gas, grain dust, and the like.